Curated OER
Triangle Inequality Theorem
High schoolers investigate the relationship between angle measures and sides of a triangle and the relationships among the three sides of a triangle. The use of technology (Cabri, Jr.) allows learners to make and test conjectures as they...
Curated OER
Midsegments of Quadrilaterals
High schoolers explore the concept of quadrilaterals as they find the midsegments of quadrilaterals using Cabri Jr. on a graphing calculator. They find midpoints, slopes, angles, and distances of lines and angles.
Curated OER
Midsegments of a Triangle
Learners analyze midsegments of triangles in this instructional activity. They use Cabri Jr. software to observe the relationships between interior angles and midsegments of triangles. Specific instructions for creating this...
Curated OER
Ratios in Right Triangles
Learners calculate the sides of right triangles in this trigonometric ratios lesson. They use Cabri Jr. software and TI-83 or TI-84 calculators to find the side lengths and their ratios to each other for various triangles. The provided...
Curated OER
Rotations in the Plane
Pupils investigate the properties of a rotation as they use technology (Cabri, Jr.) to observe the relationship between the pre-image and the image formed by the rotation. The lesson provides ample opportunity for learners to conjecture...
Curated OER
Triangles: Triangle Inequalities
Using SketchPad on their calculators to construct triangles, students measure exterior angles and remote interior angles of their constructed triangle. Students develop the triangle inequality from observation and exploration with their...
Curated OER
Connecting Translations, Reflections, and Rotations
Learners differentiate between translation, reflection and rotation. They explore the 3 types of transformation using Cabri Jr. and build on previous knowledge in this lesson.
Curated OER
Cabri Jr. - Getting Started with Triangles
Young scholars explore a basic triangle construction. In this beginning geometry lesson, students investigate the steps to necessary to create an equilateral triangle with Cabri Jr.;
That Quiz
That Quiz: Practice Test: Triangles
Test your knowledge on the attributes of triangles. There are eleven levels that may be completed with or without a timer.
Mathigon
Mathigon: Geometry: Triangles and Trigonometry: Properties of Triangles
This lesson focuses on the properties of triangles, a closed shape that has three sides, three vertices, and and three internal angles. There are different types of triangles such as a right triangle, obtuse, and acute based on the...
Mathigon
Mathigon: Geometry: Polygons and Polyhedra: Polygons
This lesson focuses on polygons; a polygon is a closed, flat shape that has only straight sides. Polygons can have any number of sides and angles, but the sides cannot be curved.
Cuemath
Cuemath: Regular Polygon
Introduces the concept of regular polygons along with regular polygon examples, not regular polygons, irregular polygons, and area of a regular polygon. Check-out the solved examples for better understanding and try your hand at solving...
Cuemath
Cuemath: Equilateral
Learn all about the basic properties of equilateral. This lesson targets the meaning of equilateral, shows how to construct equilateral shapes, explores some of the equilateral shapes and properties, and how to apply them while solving...
University of Illinois
University of Illinois Urbana Champaign: The Geometry Center: Area of Quadrilaterals
Formulas on calculating the area of a general quadrilateral and special cases of quadrilaterals.
Wolfram Research
Wolfram Math World: Math World: Hexagon
Gives a detailed overview of hexagons, particularly of regular hexagons. Be sure to use the links for unfamiliar notation or variable representation. This site gives formulas for inner radius, circumradius, parameter, and area of a...
Texas Instruments
Texas Instruments: Constructing Triangles
This activity focuses on the various ways to construct the different types of triangles such as isosceles, equilateral, right, and right isosceles triangles. Students will begin by constructing triangles based on a minimal definition of...
Texas Instruments
Texas Instruments: Isosceles Triangle
In this activity, students construct isosceles and equilateral triangles. They discover that if two sides of a triangle are congruent, then the angles opposite them are congruent. They understand that an equilateral triangle is also...
Texas Instruments
Texas Instruments: Got an Equilateral Triangle? With Cabri Jr.
Using the Compass tool in Cabri Jr., students will construct an equilateral triangle, and check the length of each side. When a vertices is moved using the Alpha hand, the triangle remains equilateral.
Texas Instruments
Texas Instruments: Isosceles Triangles
Questions on the basic characteristics of an isosceles triangle
The Math League
The Math League: Figures and Polygons
This site provides definitions of different types of polygons and figures.
Maths Challenge
Maths challenge.net: Corner Circle
This is a "three star" geometry problem where prior knowledge of circles and triangles is recommended to solve this circle in the corner problem.
Other
Generalization
Learn how to construct convex polygons and the mathematical foundations of symmetry on this site.
Math Planet
Math Planet: Geometry: Inscribed Angles and Polygons
Inscribed angles and polygons are investigated through examples and a video lesson. [0:42]